Lightweight hydrogel-bound aggregate shapes and process for producing same

Abstract

Hydrogel-bound aggregate lightweight building materials, such as blocks for use in replacement of lightweight concrete or extruded clay blocks, prepared by expanding and drying a foamable composition containing precursors for an alkali metal aluminosilicate hydrogel, fine grain particulate aggregates, and a viscosity-reducing agent sufficient to result in a starting slurry composition viscosity of less than 40,000 cps at a solids content of 70% by weight or greater.

What is claimed is: 
     
       1. A process for manufacturing lightweight, hydrogel-bound aggregate shapes having a bulk density of less than about 40 pounds per cubic foot, comprising the steps of: (a) providing a foamable composition comprised of an aqueous admixture of effective amounts of an alkali metal silicate, an alkali metal aluminate, surfactant, metal powder, particulate aggregate material and viscosity-modifying and gel-strengthening agent, said foamable composition having a total solids content of at least about 70% by weight, a total aggregate content of at least about 60% by weight, said aggregate material having a particle size distribution such that greater than about 70% thereof is of a particle size of 200 microns or less, and wherein said viscosity-modifying and gel-strengthening agent comprises finely-divided spherical particles of fumed metal oxide in an amount effective to reduce the starting viscosity of said foamable composition to less than about 40,000 cps;   (b) forming said foamable composition into a foamed, porous, self-supporting hydrogel-bound aggregate of desired configuration as a consequence of reaction between components of said composition to form a self-setting alkali metal aluminosilicate hydrogel which binds components of said composition in a self-supporting shape of desired configuration, and reaction between said metal powder and alkali materials in said composition to produce therein hydrogen gas bubbles which, in conjunction with said surfactant, develop in said composition a significant degree of porosity prior to the setting of said hydrogel; and   (c) drying said self-supporting foamed, porous, hydrogel-bound aggregate to remove moisture therefrom and produce a lightweight, hydrogel-bound aggregate shape having a bulk density of less than about 40 pounds per cubic foot.   
     
     
       2. The process according to claim 1 wherein said dried self-supporting foamed, porous, hydrogel-bound aggregate is thereafter heated to effect sintering of hydrogel-bound particulate aggregate materials therein. 
     
     
       3. The process according to claim 1 wherein said dried self-supporting foamed, porous, hydrogel-bound aggregate is fired to produce ceramic bonds therein. 
     
     
       4. The process according to claims 1, 2 or 3 wherein said lightweight, hydrogel-bound aggregate shape has a bulk density of less than about 30 pounds per cubic foot. 
     
     
       5. The process according to claims 1, 2 or 3 wherein said particulate aggregate material has a particle size distribution such that greater than about 70% thereof is of a particle size of 100 microns or less. 
     
     
       6. The process according to claims 1, 2 or 3 wherein the starting viscosity of said foamable composition is less than about 30.000 cps. 
     
     
       7. The process according to claims 1, 2 or 3 wherein said particulate aggregate material comprises partially calcined clay. 
     
     
       8. The process according to claims 1, 2 or 3 wherein said viscosity-modifying and gel strengthening agent comprises silica fume. 
     
     
       9. A lightweight hydrogel-bound aggregate, in the form of a building block, having a bulk density of about 40 pounds per cubic foot or less, made according to the process of claims 1, 2 or 3. 
     
     
       10. A lightweight hydrogel-bound aggregate, in the form of a building block, having a bulk density of about 30 pounds per cubic foot or less, made according to the process of claims 1, 2 or 3.